1. Field of the Invention
The present invention relates to a construction machine with a piping structure of pilot pipe.
2. Description of the Related Art
Conventionally, one of pilot ports of direction control valves is determined according to operating direction of an operating valve, when pilot pressure derived from the operating valve by means of a control lever is applied to the pilot ports of direction control valves. As a result, working direction of various hydraulic actuators is determined correspondingly to the operating direction of the operating valve. If operating pattern is switched, a switching valve is provided between the operating valve and the direction control valves. By switching the switching valve, the operating pattern can be switched.
In FIG. 5, an example of pilot pipe structure having the switching valve is shown. Pilot pressure derived from left/right operating valve (hereinafter, referred to as remote control valve) 19a, 19b by means of operation of a control lever not shown is applied to one of the direction control valves 4-9 selected by switching pipe ports of the switching valve 17xe2x80x2. The pilot pipes 20a, 20b extending from the switching valve 17 to the direction control valves 6-9 are provided with a pressure sensor block 17cxe2x80x2. Monitoring of pressure is carried out by means of output signal from the pressure sensors 21a, 21b provided in the block 17cxe2x80x2. 
In this case, because the pilot pipes 20a, 20b connecting the switching valve 17xe2x80x2 and the direction control valves 6-9 to each other are provided with the pressure sensor block 17cxe2x80x2, the number of pipe connecting positions and pipe assembly parts such as joints and the like becomes larger. Accordingly, arrangement of pipe becomes complex. Specifically, when pipes are required to be arranged in a small space such as a small sized hydraulic excavator, arrangement of pipes becomes more complex because of condensation of the pipe assembly parts.
The object of the present invention is to provide a construction machine with a piping structure of pilot pipe capable of decreasing the number of pipe connecting positions and pipe assembly parts such as joints to simplify arrangement of pipe.
The piping structure of pilot pipe in a construction machine according to the present invention has following construction.
The piping structure of pilot pipe comprises: a switching valve for applying pilot pressure derived from an operating valve to one of a plurality of pilot ports of direction control valves; a pressure sensor for detecting the pilot pressure; and detection ports provided in a body of the switching valve for guiding the pilot pressure to the pressure sensor.
In this case, because the body of the switching valve is provided with the detection ports for guiding the pilot pressure to the pressure sensor, the switching valve has functions of a pressure sensor block in common. As a result, the pressure sensor block need not be provided as in the conventional art. Accordingly, the number of pipe connecting positions and pipe assembly parts is decreased as many as the block. For this reason, improvement of quality and costreduction can be accomplished.
Also, because space for providing the pressure sensor block is not required, the space can be used usefully to simplify arrangement of pipe.